Most modern electronic equipment require a power supply to provide a direct current (DC) operating potential to the electronic components contained therein. Common types of electronic equipment which use power supplies include personal computers, chargers, energy systems, telecommunications, audio-video equipment, consumer electronics, automotive components, and other devices which utilize integrated circuits, semiconductor chips, or otherwise require DC operating potential. Most if not all semiconductor components require a low voltage DC operating potential. However, many sources of electric power are alternating current (AC), or high voltage DC, which must be converted to low voltage DC for the electronic equipment.
In one common arrangement, the AC/DC power supply receives an AC input voltage, e.g., between 110 and 240 VAC, and converts the AC input voltage to the DC operating voltage. The AC voltage is routed through a full-wave rectifier bridge and filtered to produce a high voltage DC signal. The high voltage DC signal is processed through a pulse width modulated (PWM) controller and transformer assembly to generate the low voltage, regulated DC output voltage, which is used as the operating potential for the semiconductor components and other devices requiring low voltage DC supply in the electronic equipment. The low voltage DC signal is typically in the range of 1 to 12 VDC. In other cases, a DC/DC power supply receives a high voltage DC signal and provides the low voltage DC signal necessary for the electronic equipment.
One known power conversion topology is known as push-pull power converter. The push-pull converter has a transformer primary side and secondary side. The secondary side of the push-pull converter typically has power transistors which switch inductor currents to charge the regulated DC output voltage. Driver transistors control the power devices during the different converter operating modes. In many cases, as discussed hereinafter, the power transistors and driver transistors must be screened and matched to achieve acceptable power conversion efficiency. The screening and matching process reduces manufacturability and increases per unit costs.
A need exists for a power converter which does not require screening and matching of the transistors on the secondary side of the transformer.